Abstract
Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool. It is of great significance to understand the dynamics of soil microbial biomass in plantation for rational management and cultivation of plantation. In order to explore the temporal dynamics and influencing factors of soil microbial biomass of Keteleeria fortunei var. cyclolepis at different stand ages, the plantation of different ages (young forest, 5 years; middle-aged forest, 22 years; mature forest, 40 years) at the Guangxi Daguishan forest station of China were studied to examine the seasonal variation of their microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) by chloroform fumigation extraction method. It was found that among the forests of different age, MBC and MBN differed significantly in the 0–10 cm soil layer, and MBN differed significantly in the 10–20 cm soil layer, but there was no significant difference in MBC for the 10–20 cm soil layer or in either MBC or MBN for the 20–40 cm soil layer. With increasing maturity of the forest, MBC gradually decreased in the 0–10 cm soil layer and increased firstly and then decreased in the 10–20 cm and 20–40 cm soil layers, and MBN increased firstly and then decreased in all three soil layers. As the soil depth increased, both MBC and MBN gradually decreased for all three forests. The MBC and MBN basically had the same seasonal variation in all three soil layers of all three forests, i.e., high in the summer and low in the winter. Correlation analysis showed that MBC was significantly positively correlated with soil organic matter, total nitrogen, and soil moisture, whereas MBN was significantly positively correlated with soil total nitrogen. It showed that soil moisture content was the main factor determining the variation of soil microbial biomass by Redundancy analysis. The results showed that the soil properties changed continuously as the young forest grew into the middle-aged forest, which increased soil microbial biomass and enriched the soil nutrients. However, the soil microbial biomass declined as the middle-age forest continued to grow, and the soil nutrients were reduced in the mature forest.
Highlights
The soil microbial biomass regulates the carbon and nitrogen cycle in terrestrial ecosystems and plays a key role in the conversion and supply of nutrients (Berg and Smalla 2009)
The first half was passed through a stainless steel filter (2 mm) and measured for soil microbial carbon (MBC) and soil microbial nitrogen (MBN), and the other half was airdried, sifted, and measured for soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), pH, bulk density (BD), and soil water content (SWC) (Oksanen 2001; Binkley and Fisher 2012).The MBC and MBN were measured by chloroform fumigation (Vance et al 1987)
For the 10–20 cm soil layer, significant difference among forests of different age was found for SOC, TN, MBC, and MBC/MBN, but did not exist for MBN, TP, pH, BD, and SWC
Summary
The soil microbial biomass regulates the carbon and nitrogen cycle in terrestrial ecosystems and plays a key role in the conversion and supply of nutrients (Berg and Smalla 2009). To ensure effective management and cultivation of plantation, it is imperative to thoroughly understand the dynamic changes of soil microbial biomass and its influencing factors during forest growth. Previous studies on the seasonal variation of soil microbial biomass in plantation mainly focused on the differences in land use pattern (Pandey et al 2010; Li et al 2018), forest type (Ravindran and Yang 2015), and forest age (Wen et al 2014). For the sake of local economy in the mountainous areas of Guangxi, it is very important to make full use of the ecological advantages of Guangxi (in both tree species resources and geographical environment) and actively develop plantation of high-valued tree species to improve the productivity of forest land. Cyclolepis plantation forests of different age at the Guangxi Daguishan forest station was studied to understand whether the changes of soil microbial biomass during the growth of K. fortunei var. The results provide a scientific basis for the rational management of K. fortunei var. cyclolepis plantation as well as cultivation of other coniferous forests in tropical and subtropical regions
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